⚡️ Speed up method ContentFile.open by 35%

[codeflash-ai]

📄 35% (0.35x) speedup for ContentFile.open in django/core/files/base.py

⏱️ Runtime : 45.2 microseconds → 33.4 microseconds (best of 648 runs)

📝 Explanation and details

The optimization changes self.seek(0) to self.file.seek(0) in the open() method. This eliminates one level of method call indirection by directly accessing the underlying file object's seek method instead of going through the parent class's method resolution.

Key Performance Impact:

• Direct method access: self.file.seek(0) bypasses the method lookup chain that would occur with self.seek(0), which needs to resolve through the class hierarchy
• Reduced overhead: The line profiler shows the seek operation time dropped from 152,366ns to 85,610ns (44% faster), contributing to the overall 35% speedup

Why this works:
In Python, method calls like self.seek(0) involve attribute lookup through the Method Resolution Order (MRO), while self.file.seek(0) directly accesses the already-resolved file object's method. Since ContentFile stores the actual I/O stream in self.file during initialization, we can safely bypass the indirection.

Test case performance:
The optimization shows consistent 20-50% improvements across all test scenarios, with particularly strong gains on:

• Large content files (40+ % faster)
• Repeated open() calls (36-39% faster)
• Empty content edge cases (28-35% faster)

This is a safe micro-optimization since ContentFile always has a valid self.file object from initialization, and the seek behavior remains identical.

✅ Correctness verification report:

Test	Status
⚙️ Existing Unit Tests	🔘 None Found
🌀 Generated Regression Tests	✅ 286 Passed
⏪ Replay Tests	🔘 None Found
🔎 Concolic Coverage Tests	🔘 None Found
📊 Tests Coverage	100.0%

🌀 Generated Regression Tests and Runtime

from io import BytesIO, StringIO

# imports
import pytest
from django.core.files.base import ContentFile
# function to test
# (copied from above, unmodified)
from django.core.files.utils import FileProxyMixin


class File(FileProxyMixin):
    DEFAULT_CHUNK_SIZE = 64 * 2**10

    def __init__(self, file, name=None):
        self.file = file
        if name is None:
            name = getattr(file, "name", None)
        self.name = name
        if hasattr(file, "mode"):
            self.mode = file.mode

    def __str__(self):
        return self.name or ""

    def __repr__(self):
        return "<%s: %s>" % (self.__class__.__name__, self or "None")

    def __bool__(self):
        return bool(self.name)

    def __len__(self):
        return self.size

    def __iter__(self):
        # Iterate over this file-like object by newlines
        buffer_ = None
        for chunk in self.chunks():
            for line in chunk.splitlines(True):
                if buffer_:
                    if endswith_cr(buffer_) and not equals_lf(line):
                        # Line split after a \r newline; yield buffer_.
                        yield buffer_
                        # Continue with line.
                    else:
                        # Line either split without a newline (line
                        # continues after buffer_) or with \r\n
                        # newline (line == b'\n').
                        line = buffer_ + line
                    # buffer_ handled, clear it.
                    buffer_ = None

                # If this is the end of a \n or \r\n line, yield.
                if endswith_lf(line):
                    yield line
                else:
                    buffer_ = line

        if buffer_ is not None:
            yield buffer_

    def __enter__(self):
        return self

    def __exit__(self, exc_type, exc_value, tb):
        self.close()
from django.core.files.base import ContentFile


# Helper functions for __iter__ (not provided in the snippet)
def endswith_cr(line):
    # Handles both bytes and str
    return (line.endswith('\r') if isinstance(line, str) else line.endswith(b'\r'))

def equals_lf(line):
    # Handles both bytes and str
    return (line == '\n' if isinstance(line, str) else line == b'\n')

def endswith_lf(line):
    # Handles both bytes and str
    return (line.endswith('\n') if isinstance(line, str) else line.endswith(b'\n'))

# Patch File to add a .chunks() method for testing
def file_chunks(self, chunk_size=None):
    # Simple implementation: yield the whole file content at once
    self.seek(0)
    data = self.read()
    yield data

File.chunks = file_chunks
File.seek = lambda self, pos: self.file.seek(pos)
File.read = lambda self, *args, **kwargs: self.file.read(*args, **kwargs)
File.close = lambda self: self.file.close()
File.size = property(lambda self: len(self.file.getvalue()) if hasattr(self.file, 'getvalue') else 0)

# unit tests

# 1. BASIC TEST CASES

def test_open_returns_self_and_resets_pointer():
    # Test that open() returns self and resets pointer to start
    cf = ContentFile("abcdef")
    cf.file.seek(3)  # Move pointer
    codeflash_output = cf.open(); result = codeflash_output # 464ns -> 281ns (65.1% faster)

def test_open_with_bytes_content():
    # Test open() with bytes content
    data = b"hello world"
    cf = ContentFile(data)
    cf.file.seek(5)
    cf.open() # 465ns -> 294ns (58.2% faster)

def test_open_multiple_times():
    # Test that open() can be called more than once and always resets pointer
    cf = ContentFile("12345")
    cf.file.seek(2)
    cf.open() # 484ns -> 293ns (65.2% faster)
    cf.file.seek(4)
    cf.open() # 248ns -> 180ns (37.8% faster)

def test_open_does_not_change_content():
    # Test that open() does not modify the content
    content = "test content"
    cf = ContentFile(content)
    cf.open() # 486ns -> 342ns (42.1% faster)

def test_open_with_name():
    # Test that name is set correctly and __str__ returns "Raw content"
    cf = ContentFile("abc", name="foo.txt")

# 2. EDGE TEST CASES

def test_open_on_empty_string_content():
    # Test open() with empty string content
    cf = ContentFile("")
    cf.open() # 510ns -> 371ns (37.5% faster)

def test_open_on_empty_bytes_content():
    # Test open() with empty bytes content
    cf = ContentFile(b"")
    cf.open() # 515ns -> 368ns (39.9% faster)

def test_open_on_content_with_newlines():
    # Test open() on content with various newlines
    content = "a\nb\r\nc\rd"
    cf = ContentFile(content)
    cf.open() # 530ns -> 359ns (47.6% faster)
    cf.seek(0)
    read = cf.read()

def test_open_with_unicode_content():
    # Test open() with unicode (non-ascii) content
    content = "üñîçødë"
    cf = ContentFile(content)
    cf.open() # 497ns -> 333ns (49.2% faster)

def test_open_with_long_name():
    # Test open() with a very long name
    long_name = "x" * 255
    cf = ContentFile("abc", name=long_name)

def test_open_after_close():
    # Test open() after closing the file
    cf = ContentFile("abc")
    cf.close()
    # open() should not fail, and should reset pointer
    cf.open() # 546ns -> 386ns (41.5% faster)

def test_open_with_non_ascii_bytes():
    # Test open() with bytes content containing non-ascii bytes
    data = b"\xff\xfe\xfd"
    cf = ContentFile(data)
    cf.open() # 502ns -> 368ns (36.4% faster)

def test_open_with_non_string_non_bytes_raises():
    # Test that passing a non-str, non-bytes content raises TypeError
    with pytest.raises(TypeError):
        ContentFile(123)

def test_open_with_none_content_raises():
    # Test that passing None as content raises TypeError
    with pytest.raises(TypeError):
        ContentFile(None)

def test_open_with_mode_argument_ignored():
    # Test that open(mode=...) is accepted and ignored
    cf = ContentFile("abc")
    codeflash_output = cf.open(mode="w"); result = codeflash_output # 781ns -> 685ns (14.0% faster)

# 3. LARGE SCALE TEST CASES

def test_open_large_text_content():
    # Test open() with a large string (close to 1000 chars)
    content = "a" * 999
    cf = ContentFile(content)
    cf.open() # 561ns -> 393ns (42.7% faster)

def test_open_large_bytes_content():
    # Test open() with a large bytes object (close to 1000 bytes)
    data = b"x" * 999
    cf = ContentFile(data)
    cf.open() # 527ns -> 393ns (34.1% faster)

def test_open_many_times_large_content():
    # Test repeatedly calling open() on a large file
    content = "y" * 999
    cf = ContentFile(content)
    for _ in range(10):
        cf.open() # 2.12μs -> 1.52μs (39.1% faster)

def test_open_and_iterate_large_content_lines():
    # Test __iter__ with large multi-line content
    lines = ["line{}\n".format(i) for i in range(500)]
    content = "".join(lines)
    cf = ContentFile(content)
    cf.open() # 524ns -> 350ns (49.7% faster)
    # Patch .chunks to yield in two large chunks
    def big_chunks(self, chunk_size=None):
        mid = len(content) // 2
        yield content[:mid]
        yield content[mid:]
    cf.chunks = big_chunks.__get__(cf, File)
    # Collect all lines via __iter__
    iter_lines = list(cf)

def test_open_and_iterate_large_bytes_content_lines():
    # Test __iter__ with large multi-line bytes content
    lines = [b"line%d\n" % i for i in range(500)]
    content = b"".join(lines)
    cf = ContentFile(content)
    cf.open() # 530ns -> 340ns (55.9% faster)
    def big_chunks(self, chunk_size=None):
        mid = len(content) // 2
        yield content[:mid]
        yield content[mid:]
    cf.chunks = big_chunks.__get__(cf, File)
    iter_lines = list(cf)
# codeflash_output is used to check that the output of the original code is the same as that of the optimized code.
#------------------------------------------------
from io import BytesIO, StringIO

# imports
import pytest
from django.core.files.base import ContentFile

# --- Function to test (from django/core/files/base.py) ---

def endswith_cr(line):
    # Helper: True if line ends with b'\r' or '\r'
    return line.endswith(b'\r') if isinstance(line, bytes) else line.endswith('\r')

def endswith_lf(line):
    # Helper: True if line ends with b'\n' or '\n'
    return line.endswith(b'\n') if isinstance(line, bytes) else line.endswith('\n')

def equals_lf(line):
    # Helper: True if line is exactly b'\n' or '\n'
    return line == b'\n' if isinstance(line, bytes) else line == '\n'

class FileProxyMixin:
    pass

class File(FileProxyMixin):
    DEFAULT_CHUNK_SIZE = 64 * 2**10

    def __init__(self, file, name=None):
        self.file = file
        if name is None:
            name = getattr(file, "name", None)
        self.name = name
        if hasattr(file, "mode"):
            self.mode = file.mode

    def __str__(self):
        return self.name or ""

    def __repr__(self):
        return "<%s: %s>" % (self.__class__.__name__, self or "None")

    def __bool__(self):
        return bool(self.name)

    def __len__(self):
        return self.size

    def __iter__(self):
        # Iterate over this file-like object by newlines
        buffer_ = None
        for chunk in self.chunks():
            for line in chunk.splitlines(True):
                if buffer_:
                    if endswith_cr(buffer_) and not equals_lf(line):
                        yield buffer_
                    else:
                        line = buffer_ + line
                    buffer_ = None

                if endswith_lf(line):
                    yield line
                else:
                    buffer_ = line

        if buffer_ is not None:
            yield buffer_

    def __enter__(self):
        return self

    def __exit__(self, exc_type, exc_value, tb):
        self.close()
from django.core.files.base import ContentFile

# --- Unit tests for ContentFile.open ---

# 1. Basic Test Cases

def test_open_returns_self():
    # Test that open() returns the ContentFile instance itself
    cf = ContentFile("abc")
    codeflash_output = cf.open(); result = codeflash_output # 557ns -> 439ns (26.9% faster)

def test_open_resets_pointer():
    # Test that open() resets the file pointer to the beginning
    cf = ContentFile("abcdef")
    cf.seek(3)
    cf.open() # 383ns -> 343ns (11.7% faster)

def test_open_with_bytes_content():
    # Test open() with bytes content
    data = b"hello world"
    cf = ContentFile(data)
    cf.seek(5)
    cf.open() # 427ns -> 349ns (22.3% faster)

def test_open_with_str_content():
    # Test open() with string content
    data = "hello world"
    cf = ContentFile(data)
    cf.seek(5)
    cf.open() # 383ns -> 349ns (9.74% faster)

def test_open_with_name():
    # Test open() with a custom name
    cf = ContentFile("abc", name="myfile.txt")

def test_open_with_empty_string():
    # Test open() with empty string content
    cf = ContentFile("")
    cf.open() # 500ns -> 390ns (28.2% faster)

def test_open_with_empty_bytes():
    # Test open() with empty bytes content
    cf = ContentFile(b"")
    cf.open() # 470ns -> 347ns (35.4% faster)

# 2. Edge Test Cases

def test_open_multiple_times():
    # Test calling open() multiple times resets pointer each time
    cf = ContentFile("abcdef")
    cf.seek(4)
    cf.open() # 390ns -> 344ns (13.4% faster)
    cf.seek(2)
    cf.open() # 262ns -> 197ns (33.0% faster)

def test_open_with_non_ascii_string():
    # Test open() with unicode content
    data = "你好，世界"
    cf = ContentFile(data)
    cf.seek(2)
    cf.open() # 377ns -> 336ns (12.2% faster)

def test_open_with_non_ascii_bytes():
    # Test open() with non-ASCII bytes
    data = "你好，世界".encode("utf-8")
    cf = ContentFile(data)
    cf.seek(2)
    cf.open() # 390ns -> 347ns (12.4% faster)

def test_open_with_mode_argument_ignored():
    # Test that mode argument is ignored
    cf = ContentFile("abc")
    cf.seek(1)
    cf.open(mode="r") # 610ns -> 571ns (6.83% faster)

def test_open_after_close():
    # Test that open() works after close()
    cf = ContentFile("abc")
    cf.close()
    # Reopen should not fail
    cf.open() # 486ns -> 362ns (34.3% faster)

def test_open_with_long_name():
    # Test open() with a long name
    name = "a" * 255
    cf = ContentFile("abc", name=name)

def test_open_with_zero_length_content():
    # Test open() with zero-length content
    cf = ContentFile("")
    cf.open() # 517ns -> 392ns (31.9% faster)

def test_open_with_large_unicode_string():
    # Test open() with large unicode string
    data = "🌟" * 1000
    cf = ContentFile(data)
    cf.open() # 505ns -> 362ns (39.5% faster)

def test_open_with_large_bytes():
    # Test open() with large bytes
    data = b"\x00\xff" * 500
    cf = ContentFile(data)
    cf.open() # 521ns -> 361ns (44.3% faster)

def test_open_with_newline_characters():
    # Test open() with newlines
    data = "line1\nline2\r\nline3\rline4"
    cf = ContentFile(data)
    cf.open() # 500ns -> 370ns (35.1% faster)

# 3. Large Scale Test Cases

def test_open_with_very_large_string():
    # Test open() with a very large string (close to 1000 chars)
    data = "x" * 1000
    cf = ContentFile(data)
    cf.open() # 495ns -> 350ns (41.4% faster)

def test_open_with_very_large_bytes():
    # Test open() with a very large bytes object (close to 1000 bytes)
    data = b"y" * 1000
    cf = ContentFile(data)
    cf.open() # 505ns -> 355ns (42.3% faster)

def test_open_with_many_open_calls():
    # Test open() repeatedly for performance and determinism
    data = "abc" * 333
    cf = ContentFile(data)
    for _ in range(100):
        cf.seek(2)
        cf.open() # 16.9μs -> 12.3μs (36.9% faster)

def test_open_with_mixed_content_types():
    # Test open() with alternating str and bytes content
    for i in range(50):
        if i % 2 == 0:
            data = "A" * (i + 1)
            cf = ContentFile(data)
            cf.open()
        else:
            data = b"B" * (i + 1)
            cf = ContentFile(data)
            cf.open()

def test_open_with_maximum_chunk_size():
    # Test open() with a chunk size close to the default
    data = "Z" * ContentFile.DEFAULT_CHUNK_SIZE
    cf = ContentFile(data)
    cf.open() # 502ns -> 366ns (37.2% faster)
# codeflash_output is used to check that the output of the original code is the same as that of the optimized code.

To edit these changes git checkout codeflash/optimize-ContentFile.open-mh6r3cou and push.